[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 190539
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON SEP 19 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM
THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON
SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM RITA IS CENTERED NEAR 23.0N 73.7W...OR 240 NM ESE
OF NASSAU BAHAMAS...AT 19/0600 UTC MOVING WNW AT 9 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1002 MB. MAXIMUM SUSTAINED WIND
SPEED IS 45 KT WITH GUSTS TO 55 KT. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC AND THE
PUBLIC ADVISORY UNDER HEADERS MIATCPAT3/WTNT33 KNHC FOR MORE
DETAILS. DEEP CONVECTION CONTINUES AROUND RITA AND THE
CONVECTIVE PATTERN REMAINS SOMEWHAT ELONGATED FROM SE TO NW WITH
THE ASSOCIATED UPPER LEVEL RIDGE ORIENTED ON THE N SIDE OF THE
SYSTEM. THE LOW-LEVEL CIRCULATION IS NO LONGER BUT IS EMBEDDED
BENEATH THE CONVECTION. SCATTERED STRONG CONVECTION IS FROM
20.5N-24N BETWEEN 69W-72.5W WITH SCATTERED MODERATE/ISOLATED
STRONG CONVECTION FROM 22.5N-25N BETWEEN 72.5W-75.5W INCLUDING
SOME OF THE S BAHAMA ISLANDS.

TROPICAL STORM PHILIPPE WAS UPGRADED TO HURRICANE AT 19/0300
UTC. HURRICANE PHILIPPE IS CENTERED NEAR 16.5N 55.9W...OR 340 NM
E OF THE LEEWARD ISLANDS...AT 19/0300 UTC MOVING NNW AT 7 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB. MAXIMUM SUSTAINED
WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. PHILIPPE IS EMBEDDED BENEATH A BROAD AREA OF
UPPER LEVEL RIDGING...BUT THE PATTERN IS BECOMING SOMEWHAT
ESTABLISHED WELL ENOUGH FOR OUTFLOW TO EXPAND TO THE S. NUMEROUS
STRONG CONVECTION IS WITHIN 45 NM OF 16.5N FROM 54.5W-57W.
SCATTERED MODERATE/STRONG CONVECTION COVERS THE REMAINDER OF THE
AREA FROM 13.5N-18.5N BETWEEN 53W-58W.

A 1009 MB LOW IS LOCATED IN THE CENTRAL ATLC NEAR 11N37W...
ALONG A TROPICAL WAVE CURVED FROM 8N36W THROUGH 16N38W TO 24N37W
AND MOVING W NEAR 10 KT. THE WAVE ITSELF IS QUITE SHARP AND HAS
BEEN PRODUCING DEEP CONVECTION NEAR ITS N END AS WELL AS JUST N
OF THE LOW-LEVEL CENTER. AN UPPER LEVEL RIDGE AXIS IS EXPECTED
TO REMAIN BETWEEN 10N-14N AND THIS WILL PROVIDE A FAVORABLE
ENVIRONMENT FOR TROPICAL CYCLONE DEVELOPMENT WITHIN THE NEXT 36
HOURS. NUMEROUS STRONG CONVECTION IS WITHIN A 30/45 NM RADIUS OF
15.5N38.5W. SCATTERED MODERATE/STRONG CONVECTION IS WITHIN
90/120 NM OF LINE 13N24W-15N38W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 20N-24N BETWEEN 32W-37.5W.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE IS ALONG 23W/24W S OF 19N MOVING W 10-15
KT. WEAK CURVATURE AS WELL AS A LOW-AMPLITUDE CIRCULATION
APPEARS ON SATELLITE IMAGERY NEAR THE CAPE VERDE ISLANDS. THE
LAST VISIBLE SATELLITE IMAGES SHOWS AN ABUNDANCE OF AFRICAN DUST
ALSO COVERING THE AREA THUS LIMITING CONVECTION ASSOCIATED WITH
THIS WAVE.

SEE SPECIAL FEATURES FOR TROPICAL WAVE/LOW ALONG 37W/38W.

CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 75W S OF 20N MOVING W
10 KT. THE LOW-LEVEL CLOUD FIELD IN THE CARIBBEAN INDICATES A
WEAK APEX JUST SW OF THE SW TIP OF HAITI...BUT THERE IS LITTLE
TO NO MOISTURE AVAILABLE FOR MARITIME SHOWERS/THUNDERSTORMS.
NUMEROUS STRONG CONVECTION HAS DEVELOPED OVER COASTAL AREAS OF
COLOMBIA AND W PANAMA BETWEEN 75W-77W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 13N15W 14N20W...THEN ALONG 10N25W
15N34W...THEN ALONG 8N38W 7N42W 10N52W. ALL CONVECTION IS
ASSOCIATED WITH THE TROPICAL WAVE AND HURRICANE PHILIPPE.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS MOVING TOWARD
THE COAST OF GUINEA BISSAU TO CENTRAL SENEGAL.

...DISCUSSION...

GULF OF MEXICO...
STRONG UPPER HIGH REMAINS ENTRENCHED FROM MEXICO TO FLORIDA...N
OF THE YUCATAN PENINSULA AND THE BAY OF CAMPECHE N TO OVER THE E
HALF OF THE UNITED STATES. THIS CONTINUES TO ADVECT A LARGE AREA
OF DRY SUBSIDING AIR OVER THE GULF WATERS AND ADJACENT LAND
AREAS. CLOUD COVER IS VIRTUALLY NON-EXISTENT EXCEPT FOR DIURNAL
THUNDERSTORMS OVER THE YUCATAN PENINSULA MOVING OVER THE E BAY
OF CAMPECHE AND OVER THE SE GULF THAT ORIGINATED OVER S FLORIDA.
HAZY CONDITION THAT COVERS NE FLORIDA EARLIER THIS EVENING HAVE
BEGUN TO CLEAR AND MOISTURE WILL BEGIN TO INCREASE LATE MON INTO
TUE WITH THE ARRIVAL OF T.S. RITA INTO THE STRAITS OF FLORIDA.

CARIBBEAN...
A LARGE AND NEARLY STATIONARY UPPER LEVEL LOW IS CENTERED NEAR
THE CAYMAN ISLANDS NEAR 20N81W WITH ITS CIRCULATION EXTENDING
FROM THE STRAITS OF FLORIDA S TO THE GULF OF HONDURAS BETWEEN
HAITI AND THE YUCATAN PENINSULA. DEEP MOISTURE IS BEING ADVECTED
E ON THE UNDERSIDE OF THE LOW...AND THE HIGHEST PRECIPITABLE
WATER VALUES EXTEND ACROSS CENTRAL AMERICA TO NEAR 75W. CLUSTERS
OF SCATTERED STRONG CONVECTION IS LOCATED INLAND OVER COSTA RICA
BUT MAINLY ON THE E PACIFIC SIDE. CLUSTERS OF SCATTERED
MODERATE/STRONG CONVECTION ARE OVER THE SW CARIBBEAN S OF 14N
FROM 78W-83W. SCATTERED SHOWERS/THUNDERSTORMS SURROUND THE UPPER
LOW N OF 15N TO OVER CUBA BETWEEN HAITI AND THE COAST OF THE
YUCATAN PENINSULA. AN UPPER LEVEL COL IS CENTERED OVER THE
E/CENTRAL CARIBBEAN WITH AN AREA OF MODERATE/STRONG SUBSIDENCE
LOCATED BETWEEN 61W-74W. CONDITIONS ALSO REMAIN DRY OVER THE
LESSER ANTILLES WITH ONLY WISPY HIGH CLOUDS MOVING FROM S TO N
ON THE PERIPHERY OF HURRICANE PHILIPPE. IF PHILIPPE REMAINS ON
TRACK...THE ISLANDS WILL BE SPARED THE HEAVIEST RAINFALL AND
WOULD ONLY HAVE TO DEAL WITH OCCASIONAL SHOWERS IN THE COMING
DAYS.

WEST/CENTRAL ATLANTIC...
AN INVERTED UPPER LEVEL TROUGH...AN EXTENSION OF THE UPPER LOW
NEAR THE CAYMAN ISLANDS...STRETCHES ACROSS CENTRAL CUBA TO THE
NORTHERN BAHAMAS...JUST AHEAD OF T.S. RITA. ABUNDANT DRY AIR IS
MOVING FROM NE TO SW FROM THE NW ATLC ACROSS FLORIDA TO THE W OF
THE TROUGH...BUT THIS FEATURE APPEARS TO BE ISOLATED THE DRIEST
AIR AWAY FROM RITA. A WEAK UPPER LEVEL HIGH IS E OF RITA NEAR
23N69W WITH A MODERATE OUTFLOW JET EXTENDING ALONG 22N/23W E
INTO THE CENTRAL ATLC. AN UPPER LEVEL SHEAR AXIS LIES N OF THIS
JET ALONG 28N70W 25N54W 26N46W 25N38W AND SEPARATES THE UPPER
MOISTURE OF RITA FROM DRY AIR ON THE S SIDE OF A LARGE UPPER
HIGH CENTERED NEAR 37N55W. A SURFACE TROUGH IS LOCATED ABOUT 500
NM E OF RITA AND ALTHOUGH IT IS UNDER STRONG WESTERLY SHEAR FROM
THE OUTFLOW JET...IT IS STILL PRODUCING AN AREA OF SCATTERED
THUNDERSTORMS FROM 17N-26N BETWEEN 60W-65W. ELSEWHERE...A LARGE
UPPER HIGH HAS DEVELOPED OVER PHILIPPE NEAR 15N54W WITH THE BEST
OUTFLOW EXTENDING E AND S OF THE SYSTEM.

EAST ATLANTIC...
AN UPPER LEVEL RIDGE STRETCHES ACROSS THE TROPICS ALONG 14N FROM
PHILIPPE E TO THE CAPE VERDE ISLANDS AND IS PROVIDING A
RELATIVELY LOW SHEAR ENVIRONMENT BETWEEN 10N-20N...THE MAIN BELT
OF TROPICAL WAVE PROGRESSION. STRONGER UPPER LEVEL WESTERLIES
ARE LOCATED N OF 20N...AND THIS PATTERN MAY FOSTER ADDITIONAL
TROPICAL CYCLONE DEVELOPMENT OVER THE NEXT SEVERAL DAYS IN THE E
ATLC. AN UPPER LEVEL TROUGH IS LOCATED FARTHER N FROM THE AZORES
SW TO 27N42W...AND THIS FEATURE WILL BEGIN TO AMPLIFY IN THE
NEXT 3-4 DAYS CAUSING HIGHER SHEAR VALUES E OF 42W.

$$
WALLACE


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